Method of making contacting column

ABSTRACT

Disclosed in a small diameter contact column having a vertical series of contact chambers separated by perforate plates. Fully erected columns of this type are substantially inaccessible for subsequent placement and attachment of internal parts. The column is achieved by superimposing a plurality of interengaging cylindrical sections adapted along their outermost engaging edges to be rigidly joined and along their innermost engaging edges to receive and support a perforate plate. The perforate plate support means permits free relative movement of the plate due to temperature change and at the same time prevents liquid from passing between the column wall and the peripheral edge of the perforate plate.

United States Patent ml 3,590,475

[72] Inventors Jacob M.Geist [56] References Cited Allentown; UNITED STATES PATENTS Roy A. Paul, Bethlehem, Pa.; Robert M.

Thorogood. West l-lorsely. Surrey. England 212 412 l 3,195.229 7/1965 Culver 29 ed I 3,235.344 2/1966 Dreyer m1. 23/289 [45] Patented July 6,1971 [73] Assignee Air Products and Chemicals, Inc. FOREIGN PATENTS Allentown, Pa. 964,441 9/1964 Great Britain. 202/l58 Continuation of application Ser. No.

P E '-JhF.C bll 585,796, 0ct.ll. 1966, now abandoned. 0 amp e Assistant ExaminerRichard Bernard Lazarus Attorneys-Ronald B. Sherer, James C. Simmons and B. Max

Klevit ABSTRACT: Disclosed in a small diameter contact column having a vertical series of contact chambers separated by perforate plates. Fully erected columns of this type are substantially inaccessible for subsequent placement and attachment [54] METBOD 0F I CONTACTING COLUMN of internal parts. The column is achieved by superimposing a 2Cla'ms3 Draw'ng plurality of interengaging cylindrical sections adapted along [52] [1.8. CI 29/471.l, their outermost engaging edges to be rigidly joined and along 29/482, 29/483 their innermost engaging edges to receive and support a per- [51] lnt.Cl B23k 31/02 forate plate. The perforate plate support means permits free [50] Field of Search 29/47 1.1, relative movement ofthe plate due to temperature change and 472.l,472.3,475,482,483;26l/ll3,114,108; at the same time prevents liquid from passing between the 202/158 column wall and the peripheral edge of the perforate plate,

PATENTED JUL 6 I971 SHEET 1 OF 2 FIG. I.

JACOB M.GEIST, ROY A PAUL and ROBERT M. THOROGOOD IN VUNTORS ATTORNEY PATENTEU JUL 5 l97| SHEET 2 OF 2 JACOB M GEIST, ROYA. PAUL 0nd ROBERT M. THOROGOOD IN VIL'NTURS ATTORNEY METHOD OF MAKING CONTACTING COLUMN CROSS-REFERENCES TO RELATED APPLICATIONS BACKGROUND OF THE INVENTION Contact columns having contact plates or trays can be used to separate the components of a liquid mixture toscrub gases or vapors with liquids and for fractionation of liquefied gases such as rectification of liquid air.

Contact columns of narrow diameter, particularly those columns used in rectification of cryogenic fluids pose special design problems in obtaining operational efficiency. In wider columns of 36 or more inches having sufficient operating space for workmen inside thereof, a complete outer shell can be utilized and the inner parts, such as trays and the like, can be later fitted and sealed within the shell. These procedures cannot be utilized in connection with columns of smaller diameter, e.g., on the order of about 18 to 24 inches. In forming contact columns of small diameter, the conventional practice is to use thin copper trays of dish or bowllike shape which are stacked one above the other in nesting relation and sealed by soldering at the peripheral edges of the dishes. The assembled and united stack of trays is mounted within an enclosing shell and the assembled structure is then fitted and fixed into an outer enclosing secondary shell or pressure-proof vessel. Since the connecting conduit lines for introduction and removal offluids into and from the column are generally made of metals other than copper, transition pieces and special flanges are required at the joints between the different metals. The soldered joints between trays and elsewhere also provide problems in maintaining firm fluid seals. Construction of this type, it will be appreciated, is comparatively costly. Substitution of aluminum for the copper dish trays in structures of this type is not feasible because of the inherent difficulties in soldering aluminum; whereas, welding presents added problems from the standpoint of buckling due to the high temperatures required.

SUMMARY OF THE INVENTION It has been found that narrow contact columns can be constructed of a light metal such as aluminum or magnesium by providing a series of vertical interengaging chambers (rings) with perforate plates disposed between each chamber. The vertical chambers are so constructed that they can be circumferentially welded without distortion of the shell or the perforate plate. The plates are disposed in a recess provided by a shelf in the wall of one ring and closed by the mating of ad jacent chambers (rings) in a manner so as to be able to freely expand and contract in service and at the same time maintain a fluid seal between the peripheral edge of the plate and the wall of the column.

The primary object of the present invention is to provide a small diameter column made of a light metal of high efficiency and good structural stability which can be economically produced.

A further object of the invention is to provide a method of assembly of such contact columns by welding of component parts without distortions ordinarily accompanying thermal stresses.

Another object of this invention is to provide a contact column wherein the trays are so supported that they can move laterally in response to thermal contraction and expansion and thus prevent buckling of the trays and column while, at the same time, maintaining a sufficiently small clearance between the trays and column walls so as to prevent liquid bypass when the column is in service.

It is another object of this invention to provide a contact column constructed entirely of aluminum, magnesium, or other light metals.

It is another object of this invention to provide contact columns of sufficient integral strength so as to eliminate the need for secondary shells.

It is still a further object of this invention to provide an assembly procedure wherein all assembly operations can be performed without the necessity of a workman entering the column.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is an elevation view, partially in section of a fragmentary portion of a contact column embodying the preferred form of the nested ring construction.

FIG. 2 is a section taken along lines 2-2 of FIG. 1 showing the construction of a typical contact tray and illustrating the relative positions of its downcomer opening, weir and baffles.

FIG. 3 is an enlarged view partly fragmentary and partly in section of a full ring and a portion of an adjacent ring illustrating details of the method for fastening adjacent pillar sections.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. I there is shown a contact column of about 24 inches inside diameter comprising a plurality of chambers or rings 10, 12, 14, l6, l8, and 20. Each ring is identical in size and formed of a light metal such as aluminum or magnesium although other materials of construction may be employed. Each ring is preferably cylindrical in shape with an outer surface 22 and an inner surface 24 defining a wall 26 therebetween as shown in conjunction with ring 16 of FIG. I.

A portion of surface 24 is removed from the top and a portion of surface 22 is removed from the bottom of each ring to provide reduced wall sections 28 and 30 respectively. The reduced wall portions 28 and 30 are the same configuration for each ring so that a plurality of rings can be assembled in a stacked relationship with a resulting uniform inside and outside diameters for the assembled column. The type of joint resulting from the reduced wall portions of adjacent rings is commonly referred to as a lap joint. Reduced wall portions 28 and 30 are further provided with chamfered surfaces 32, 34 to define a groove between adjacent rings [e.g. I4 and 18 respectively). Adjacent rings 14 and 18 are also provided with similar chamfered surfaces 33, 35 respectively so that a V- groove is achieved between adjacent rings. The V groove can then be used to circumferentially join adjacent rings as by placing therein welds 36, 38 respectively. Other joining means can be employed depending upon the operating environment of the column; however, for a column constructed of aluminum for cryogenic fluids, conventional aluminum metal girth welds are preferred.

There is also formed on surface 24 a second portion of reduced wall thickness 40 which defines a shelf 42 for supporting tray 44 as will hereinafter be more fully described. The reduced wall section 40 is intermediate in thickness between reduced wall section 28 and wall 26. Shelf 42 and the bottom surface 46 of wall 26' of ring 14 thus form a peripheral recess for positioning of the tray 44 in the column. Reduced wall section 40 is formed with an axial length just sufficient to allow expansion of the tray from heat generated by circumferential weld 36 being put in place. It is also sized so that if the column is used with cryogenic fluids the space between the tray 44 and reduced wall section 40 will not be large enough to pass fluid to the chamber defined by surface 24 of ring 16.

The rings are conveniently formed from aluminum plates cut to appropriate lengths which are rolled into cylindrical sections and welded along their length. The configurations of the reduced wall sections 28, 30, 40, including the shelf 42, may be formed during forming of the rings or may be conveniently machined into the formed and welded rings. The rings with reduced wall sections can also be formed by other conventional metalworking techniques such as casting, forgoing, extruding, etc., in conjunction with machining.

Perforate circular trays 44, 48, and 50 also preferably formed of aluminum, are adapted to be received and supported on shelves 42, 52, and 54 of rings 16, I8, and 20 respectively, within annular recesses formed as described above between the respective adjacent rings. In the embodiment described, the radial dimension of each tray is about 0.12 inches less than the radial dimensions of reduced wall section 40 formed in wall 26 of ring 16. This dimensional difference between a tray and its respective reduced wall section allows for different size changes in the column proper and trays during welding or in use, while at the same time preventing buckling of the trays. The vertical height of each recess after welding is about 0.0l inches greater than the thickness of the trays which is about one sixteenth of an inch. The gap formed between the top of the trays and the bottom of the wall of the adjacent ring is so small that liquid will not flow therethrough. The gap between the top of tray 44 and surface 46 can be accurately measured after the rings 14 and 16 have been joined by the weldment 36.

1 Referring to FIGS. 1 and 2, it can be seen that typical tray 44 includes a central opening 56, a major surface 58 having perforations 60 therein, a downcomer opening 62 and a nonperforate annular sector 64. The downcomer position thereabove is shown in phantom lines to the right of opening 62 of tray 44 (FIG. 2) while the downcomer opening in the tray 48 therebelow is shown in dotted outlines to the left of opening 62. The perforate region 58 occupies the major portion of tray 44 and extends from a low inlet weir 66 counterclockwise to an outlet weir 68 of the same height. The downcomer opening 62 is positioned angularly between outlet weir 68 and a substantially higher baffle 70. The nonperforate sector 64 is located angularly between the high baffle 70 and the low inlet weir 66. As can be seen in FIG. 1, the outlet weir 68, baffle 70 and the inlet weir 66 are all positioned on the upper surface of tray 44. A downcomer conduit 72 is located on the underside of tray 44 and circumscribes the downcomer opening 62. The elements 66, 68, 70, and 72 are fixedly secured to and supported on the tray 44 in any convenient manner such as by riveting or welding.

Flexible tab 74 of substantially the same height as weir 68, is

' secured along its outer edge to the weir 68. The tab forms a fluidtight joint with the weir. The outer edge of tab 74 abuts the inner wall of ring 14 of the column in fluid sealing relationship therewith. If desired, the other edge of weir 68 may also be provided with a rigid or flexible tab 76 adjacent pillar 78, which will be described in detail hereinafter. Tabs 80 and 82, at least one of which is flexible, of the same length as the tall baffle 70 and one or more tabs 84 and 86, at least one of which is flexible, of the same length as the low inlet weir 66 are also provided. Tab 80 forms a flexible fluidtight joint between baffle 70 and inner wall of ring 14 and tab 82 forms a fluidtight joint between baffle 70 and pillar 78. Tab 84 forms a flexible fluidtight joint between weir 66 and the inner wall of ring 14 and tab 86 forms a fluidtight joint between weir 68 and pillar 78. The tabs 74, 80, and 84 which form fluidtight joints between the respective baffle and weirs and the inner wall of ring 14 permit relative radial movement between tray 44 which supports baffle 70, and weirs 66 and 68 and the column proper. The tabs can be formed of any material that will remain flexible under operating conditions. For cryogenic applications, thin metal (e.g. aluminum) tabs are satisfactory.

in addition to the rings and trays, the contact column includes central cylindrical pillar sections 78, 88, 90, and 92. Referring now to FIG. 3 it can be seen that each pillar section is formed with a collar 94 and an inner shaft 96 having a threaded extension 98 at one end adapted to extend through the opening 100 of tray 48. A complementary threaded recess 102 is provided at the other end of shaft 96. Each shaft is connected to its respective collar by an annular plate 104. The dimensions of the collars and shafts are so related to the dimensions of the rings and trays that the adjacent shafts, when interthreaded, will cause their respective collars to tightly clamp the trays with which they are assembled. For example, tray 48 is tightly clamped by collars 88 and 90 when the threaded extension 98 of shaft 96 is inserted in the threaded aperture 106 of shaft 108 of pillar 90.-

While the liquid vapor contact trays of the type illustrated in FIGS. l and 2 are preferred, it will be understood that the essential features of the invention can be utilized with columns having vapor-liquid contact trays other than of the sieve or perforated bottom type, such as trays provided with bubble caps, valved openings, or other types known in the art. Moreover, with any type of tray employed, the central pillar can be omitted and the whole surface of the tray utilized for vapor-liquid contact, with or without localized liquid downcomer or withdrawal openings.

In addition to the ring, tray, and pillar units described above, the contact column includes a conventional top closure and bottom closure (not shown) fitted with the usual conduits for entry and removal of fluid.

The operation of the contact column when employed for example, in the rectification of liquid air is as follows: Vapors from above the liquid on a first liquid-vapor contact tray move upwardly through the perforations of the tray above and bubble into the liquid contained thereon. The liquid on the first tray received from the downcomer of the tray above travels (counterclockwise in the illustrated embodiment) along an annular passageway on the tray around the pillar. In its travel, the liquid receives vapors from below through the perforations of the first tray and loses vapors to the space thereabove. The liquid on the first tray flows over the weir through the downcomer opening of the first and onto the imperforate sector of the tray below. Each lower tray is oriented with respect to the tray above so that the nonperforate annular region thereof is directly beneath the downcomer of the tray immediately thereabove. The liquid seal'between the trays and recesses in the column proper provided by their relative dimensions eliminates, for all practical purposes, leakage of liquid down the inner wall of the column. Such seal is effected by reason of the surface tension of the liquid and the pressure differential across the narrow gap between the top of the tray at its peripheral edge and the recess in which it tests.

A preferred-method for assembly of the column will now be described with reference to the specific embodiment illustrated in the drawings; This type of column can be readily assembled employing a lathe-type setup utilizing a welding positioner and retractable support rollers movable along the lathe bed between the lathe head and tailstock.

A first ring, for example ring 20 shown in FIG. 1, having a pillar section 92 arranged concentrically therein is positioned in a chuck on the lathe head with its lower end (as seen in FIG. 1) held by the chuck. The first tray 50 is then placed on shelf 54 and over the top of pillar section 92, care being taken to assure proper orientation of the tray. The threaded extension (not shown) of pillar section is then inserted through the central opening of tray 50 and is screwed into the female threaded recess of the shaft (not shown) within pillar section 92 thus tightly clamping tray 50 between the opposed edges of the collars of pillar sections 90 and 92. Pillar sections 90 and 92 now hold tray 50 with its downcomer in correctly oriented position. The second ring 18 is now inserted into the exposed' end of ring 20 with the reduced wall section at the bottom of ring 18 nested within the reduced wall section at the top of ring 20 forming a lap or rabetted joint.

The tailstock of the lathe is advanced to initially engage the distal end of the second ring 18, after making sure that the bottom of ring 18 is properly mated with the top of ring 20. The tailstock is then advanced further to exert firm pressure between the seated rings. Now the rings are welded in their nested relation by applying a girth weld as shown at 110 within the V-groove formed by chamfering the adjacent outermost surfaces of adjacent rings. Such welding can be accomplished in a conventional manner using a torch mounted in fixed position on a translatable carriage, while rotating the sections held between the lathe stocks.

After welding together the first two cylindrical sections having the first tray therebetween, the assembled portion of the column is laterally supported by retractable rolls and the tailstock backed off to provide access within the second ring and tray 54 as tray 48 is clamped and held in position by pillar 88.

Ring 16 is then fitted into ring 18. The tailstock is advanced to press ring 16 against ring 18 and the weld 38 is made.

' Thereafter the tailstock is backed off and the tabs are installed and secured by bolts or rivets.

Other trays, pillars, and rings are added to the assembly as were ring 16, tray 48, and pillar 88. Thereafter the assembled rings may be removed from the lathe and the top closure and bottom closure welded or otherwise attached to the ends thereof.

During initial assembly, the height of the reduced wall section (e.g. 40 of FIG. 1) defining the tray supporting recess of the column is somewhat greater than that required, so that the gap between the top of a tray and the overhanging bottom of the next adjoining ring is larger than the desired tolerance. During welding of the ring sections, the rings are drawn together more tightly, thus shrinking the distance between ring and tray thereby providing the desired tolerance permitting lateral movement of the edge of the tray while maintaining the desired liquid seal between the periphery of the tray and its supporting recess.

Having thus described our invention by what is considered to be the preferred embodiment, we wish it understood that it is to be limited only by the scope of the appended claims.

We claim: 7

l. A method of fabricating a welded contact column having vapor-liquid contact trays supported therein, the assembly being arranged to permit relative movement between column and tray structure sufficient only to prevent distortion and buckling of the latter resulting from expansion or contraction of the column and tray during fabrication or in service without sacrificing the fluid seal between the contact tray and column, said method comprising the steps of:

providing a plurality of rings having complementary end portions adapted for end-to-end interengagement, the inner perimeter at the upper end of each ring having a tray-supporting shelf and the outer perimeters at the top and bottom of the ring being chamfered;

seating on the shelf of a first ring a circular tray whose diameter and thickness are such as to provide top and side clearance on the shelf;

nesting a second ring on top of the first ring, in interlocking engagement therewith, whereby the bottom end surface of the second ring overhangs the shelf of the first ring to lock the tray loosely in a recess, and the opposed chamfered surfaces form a circumferential groove;

applying endwise pressure to the assembled rings;

depositing weld metal in the circumferential groove to unite adjacent rings, the clearance provided between the edge of the tray and the confining surfaces of the recess being sufficient to accommodate the differential expansion resulting from the high temperatures obtained by welding, without buckling the tray;

and repeating said steps until the desired number of column sections are assembled.

2. A method as in claim 1, including the steps of inserting cylindrical spacers between trays before seating a tray on its shelf, said spacers having complementary threaded elements at their opposite ends, the male element of which projects through a central opening provided in the tray, and screwing the spacers together to clamp the trays into a unitary tray assembly. 

1. A method of fabricating a welded contact column having vaporliquid contact trays supported therein, the assembly being arranged to permit relative movement between column and tray structure sufficient only to prevent distortion and buckling of the latter resulting from expansion or contraction of the column and tray during fabrication or in service without sacrificing the fluid seal between the contact tray and column, said method comprising the steps of: providing a plurality of rings having complementary end portions adapted for end-to-end interengagement, the inner perimeter at the upper end of each ring having a tray-supporting shelf and the outer perimeters at the top and bottom of the ring being chamfered; seating on the shelf of a first ring a circular tray whose diameter and thickness are such as to provide top and side clearance on the shelf; nesting a second ring on top of the first ring, in interlocking engagement therewith, whereby the bottom end surface of the second ring overhangs the shelf of the first ring to lock the tray loosely in a recess, and the opposed chamfered surfaces form a circumferential groove; applying endwise pressure to the assembled rings; depositing weld metal in the circumferential groove to unite adjacent rings, the clearance provided between the edge of the tray and the confining surfaces of the recess being sufficient to accommodate the differential expansion resulting from the high temperatures obtained by welding, without buckling the tray; and repeating said steps until the desired number of column sections are assembled.
 2. A method as in claim 1, including the steps of inserting cylindrical spacers between trays before seating a tray on its shelf, said spacers having complementary threaded elements at their opposite ends, the male element of which projects through a central opening provided in the tray, and screwing the spacers together to clamp the trays into a unitary tray assembly. 